Rotary pumps or compressors



June 9, 1956 F. w. M COMBIE 2,750,896

ROTARY PUMPS OR COMPRESSORS Filed Feb. 10, 1955 2 Sheets-Sheet l INVENT OR ATTORNEY June 9, 1956 F. w. M COMBIE 2,750,896

ROTARY PUMPS OR COMPRESSORS Filed Feb. 10, 1953 2 Sheets-Sheet 2 INVENTOR FEEDER 1' CA W, H Cfl/YBIE ATTOHQEY United Sates Patent Office ROTARY PUMPS OR COMPRESSORS Frederick W. McCombie, London, England, assignor to Megator Pumps & Compressors Limited, London, England Application February 10, 1953, Serial No. 336,170

Claims priority, application Great Britain February 15, 1952 3 Claims. (Cl. 103-216) This invention relates to rotary pumps or compressors of the kind including a displacement chamber mounted for reciprocating movement within the pressure chamber of the pump or like casing, an eccentric rotatably mounted within said displacement chamber and engaging the walls of the latter at two oppositely disposed points on the periphery of the eccentric to provide a substantially fluidtight seal and by virtue of its rotational movement within said chamber give rise to the desired displacement effect, said displacement chamber being mounted for reciprocating movement in the plane of rotation of the eccentric and in contact with a guiding surface located within the casing, the displacement chamber and guiding surface being formed with co-operating ports which under the reciprocating action of the displacement chamber control the flow of fluid to and from the chamber. Such a construction of pump or compressor forms the subject of prior Patents Nos. 2,561,808; 2,561,809 and 2,561,810. It will be appreciated that a pump of larger capacity can be constructed by providing any number of such displacement chambers each associated with its own particular eccentric.

The displacement chamber in the particular class of pump or compressor with which the present invention is concerned may take the form of a hard rubber, plastic or other component which in side elevation is substantially of U-shape, the displacement chamber being usually termed a shoe and for convenience being hereinafter referred to as a shoe in the ensuing description, the shoe being of hollow construction open at one end to accommodate the eccentric and closed at'the opposite end, with a port or ports passing through the closed end for connection alternately with inlet and outlet ports formed in a plate (hereinafter referred to as the port plate) with which the shoe is in facial contact, the shoe being maintained in sealing engagement with the port plate by the pressure of the fluid in the pump casing acting on the'shoe.

Hitherto it has been the practice to mould said shoe in one piece from hard rubber or other suitable mouldable material. This had certain disadvantages both in the production or fabrication of the shoe and its utility or use in operation.

Having in mind the defects of the prior art shoes, it is an object of the present invention to provide a displacement chamber shoe that is easy to produce and fabricate.

It is another object of the invention to provide a displacement chamber shoe having accuracy of dimensions.

It is a further object of the invention to provide a displacement chamber shoe having improved eiiiciency in operation.

It is still another object of the invention to provide a displacement chamber shoe having ruggedness and universatility of use in handling different types of fluids.

A shoe for use in a rotary pump or compressor of the kind set forth is in accordance with the present invention formed in two or more parts.

It is preferred to construct the shoe in two halves the division lying in a plane passing through the centre of the eccentric and corresponding to the plane of rotation of the eccentric.

By dividing the shoe into two or more parts in a plane or planes parallel to the plane of rotation of the eccenric the mouths of the inlet parts may readily be made much wider than the internal width of the shoe which corresponds to the thickness of the eccentric, there being no difficulty in extracting the inner portion or core of the mould such as would occur if a shoe of such design were moulded in one piece.

It is preferred that each shoe shall include a liner and outer shell the liner being made of a material differing in properties from the material of the shell, so that the internal and external working surface of the shoe may be of the material most suited to their different working conditions.

For example, the shell may be of a comparatively rigid material to enable it to resist high pressure and to maintain a fiat surface over the ports in the port plate while the liner may be of resilient material to ensure a closer fit on the rotor. The shell may be made, for example, of ebonite or synthetic resin composition and the liner of natural or synthetic rubber. The liner may, like the shell be formed in a number of parts and it is preferred to mould each shell part with an integral liner part or alternatively to mould the liner in one piece and to mould the shell in two or more parts which are assembled around the liner and detachably or permanently secured together. in such a case the liner if removable can readily be replaced when worn.

In order that the invention may be clearly understood and readily carried into effect the invention is hereinafter described with reference to the accompanying drawings in which:

Figure l is a fragmentary vertical section of a rotary pump fitted with a shoe constructed in accordance with the invention.

Figure 2 is a side elevation of the shoe removed.

Figures 3 and 4 are vertical and horizontal sections respectively on the lines A-B and CD in Figure 2.

accommodate a separately formed liner.

Figure 7 is a vertical section on the line EF in Figure;- 6 showing both halves of the shoe and the contained linen Figures 8 and 9 illustrate the liner in side and rear elevation.

Referring in the first case to the construction of shoe; illustrated by Figures 1 to 4, the shoe is in the form of a two-part moulding, each half comprising an outer shell part 1 and a liner part 2, the shoe being of substantially U-shape in side elevation so that it partly embraces an associated eccentric or rotor disc 3 carried by a shaft 4, the rotation of the eccentric imparting the necessary reciprocating upward and downward movement to the shoe relative to a plate 5 associated with the casing of the pump or compressor, the plate being provided with inlet and outlet ports indicated by reference numerals 6 and 7 which further co-operate with ports 8 and 9 in the shoe. It is preferred to produce the shoe and its associated liner from a natural or synthetic rubber, the composition of the material in the case of the linear being slightly different from that of the shell, the two compositions being introduced into the mould simultaneously so that when the. composite shell and linear are cured the liner will be com-.

paratively resilient in relation to the shell. It will be appreciated, therefore, that the linear and shell will be inseparably connected together.

The shoe parts may be connected together by bolts or other securing members or secured together by means of an adhesive or a bonding process. In the construction,

shown the shoe is formed. in two parts, the central division line passing h ou h the seatre at the eesentr e and ear: respondingto the plane of rotation of the eccentric.

In the alternative construction illustrated by Figures to 9, the liner 2 in this case is moulded separately from the shell 1, this construction having the advantage that the liner can be easily removed for replacement purposes.

As will be seen clearly from Figure 6 each shell part 1 is recessed as at to accommodate half the liner 2, the latter fitting closely within the two complemental recesses and thus serving to maintain the two halves of the shell in correct register. As an alternative to bonding the two halves of the shoe together, they may be connected by means of a series of bolts which are not illustrated, but which are inserted through holes 11 formed in the shell parts, the holes being preferably countersunk to accommodate correspondingly shaped bolt heads and nuts so that the shoe has a smooth external configuration.

As in the previously described arrangement the ports 8 and 9 can be made of considerably increased width at their mouths and furthermore as in the previously described construction the liner 2 may be of a material quite different from that from which the two shell halves are formed. For example, the liner may be moulded from a natural or synthetic rubber composition Whilst the shell halves can be moulded from a comparatively hard material, such as for example, ebonite or synthetic resin composition with or without a mineral or vegetable filler.

Figure 4 shows clearly how the Width of the mouths of the ports can be increased by making the shoe in a number of parts divided in a plane parallel with the axis of rotation of the eccentric, the same advantage being obtainable with the construction shown in Figures 5 to 9. In the case of a shoe moulded in one piece the ports could not readily be produced in this form owing to the difliculty of extracting the inner portion of core of the mould. Furthermore, making the shoe in two halves instead of moulding it in one piece has a great advantage in production as the halves take the form of flat and comparatively shallow mouldings which do not necessitate the use of an internal core. This facilitates filling the mould uniformly, ensures uniform density of the material throughout and enables each moulding to be easily extracted from the mould without damage or distortion.

As regards the port formation the ports may be so dimensioned as to permit of the pump being operated at a higher speed and thus have a larger capacity. In this connection with a rotor having eccentrics of a given diameter, eccentricity and width, the speed and capacity are limited by the permissible velocity of the fluid through the ports. The velocity is determined by the effective area of the ports which equals the eccentricity (or movement of the shoe away from the centre position) multiplied by the width of the ports. By making ports in the shoe of tapered formation and so increasing their effective width, it is therefore possible to rotate a pump of given rotor dimensions at a higher speed. This enables a pump of given capacity t be made smaller and cheape nd to be coupled directly to faster-running, and therefore cheaper prime movers.

A second advantage of the increased width of the ports is that the total area of the ports can be made substantially al to the ensuing at the the an e th Shoe, that is, to the projected area of the rotor disc. During he s s n ke th arres s s e the o i lower n li amb? (pres re and if t e a ea o t pa is less than the projected area of the disc there is an unbalanced force in the interior of the shoe tending to draw it in the direction'in which the disc is travelling, that is to say, away from the port plate. The equalisation of open areas at the two ends of the shoe therefore helps to keep the shoe in close contact with the port plate during the suction stroke. M i

I claim:

1. A displacement chamber for use with an eccentric rotor of a rotor pump or compressor, comprising an outer shell, a liner for said shell, said liner being made of a material differing in resilience from that of the shell, said shell and said liner having ports for receiving said rotor, the mouths of said ports being of greater diameter than the width of said rotor, said shell and said liner each comprising two sections and the dividing line for the sections being contained in a plane perpendicular to the axis of rotation of the rotor and medial of the width of the rotor, and means for securing said sections in fixed relation to each other. i l

2. A displacement chamber for use with an eccentric rotor of a rotary pump or compressor, comprising an outer shell, a liner for said shell, said liner being made of a material differing in resilience from that of the shell and being of unitary construction, said shell and said liner having ports for receiving said rotor, the mouths of said ports being of greater diameter than the width of said rotor, said shell being divided into two sections and the dividing line for said shell being contained in a plane perpendicular to the axis of rotation of the rotor and medial of the width of the rotor.

3. A displacement chamber for use with an eccentric rotor of a rotary pump or compressor, comprising an outer shell, a liner for said shell, said shell and said liner having ports for receiving said rotor, the mouths of said ports being of greater diameter than the width of said rotor, said shell being divided into two sections and the dividing line for said shell being contained in a plane perpendicular to the axis of rotation of the rotor and medial of the width of the rotor.

Humphrey c7 I an. 24, 1922 McCombie July 24, 1951 

